[llvm-readobj] Option to emit readelf like output

New option --elf-output-style=LLVM or GNU
Enables -file-headers in readelf style when elf-output-style=GNU

Differential revision: http://reviews.llvm.org/D14128

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@260391 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed